The invention relates to “active implantable medical devices” as defined by Directive 90/385/EEC of 20 Jun. 1990 of the Council of the European Communities, specifically the detection of electrical potentials generated by organs and/or electrical stimulation of these organs, in particular cardiac diagnostic and therapy applications.
However, although in the following mainly a cardiac detection/stimulation system is described, this application is not limitative of the invention which, as will be understood, may also be applied, mutatis mutandis, to the detection/stimulation of other organs such as the nervous system (including brain stimulation or nerve stimulation), the arterial or lymphatic system, the digestive system (stomach, intestine) or the respiratory system.
In the case of the heart, the invention relates more particularly to the situation of patients with Heart Failure (HF), to which the implantation of a cardiac resynchronization device of the CRT-P type (pacemaker) or CRT-D type (pacemaker with also defibrillator function) is proposed.
The therapy aims to resynchronize the contraction of both ventricles between them, and if necessary one of the ventricles relative to the atrium in order to improve the patient's condition by optimizing the phases of the hemodynamic cycle. For this, the devices implement a technique called “CRT” (Cardiac Resynchronization Therapy) or “BVP” (Bi-Ventricular Pacing) of issuing as necessary electrical pulses ensuring joint and permanent stimulation of both the left and right ventricles to resynchronize the contractions of the latter.
Regarding the implanted device, it requires the implantation in the right ventricle of a conventional endocardial pacing lead and for the stimulation of the left ventricle of a lead inserted into the coronary venous system CVS via the coronary sinus, so as to place the pacing electrode of this lead against the wall of the left ventricle. An alternative is to use an epicardial lead as the left ventricular lead, introduced into the pericardial sac and secured to the outer wall of the heart muscle. The device also often provides the implementation of a third lead positioned in the right atrial cavity, for detecting the contraction of the atrium in order to synchronize on it the stimulation of the ventricles, by respecting the chronology of the atrioventricular delay.
These endocardial or coronary leads are introduced through the patient's venous system, which can lead to complications such as displacement, insulation or conductor breakage, fibrosis development, etc.
To reduce these risks, a new generation of devices has been developed, which are in the form of implantable autonomous capsules in a heart chamber (ventricle, left atrium or even arterial left cardiac chamber) and are generally referred to as “leadless capsules.” These capsules are devoid of any physical connection to a main implantable device (such as the housing of a stimulation pulse generator) or non implantable device (external device such as a programmer or a monitoring device for patient remote monitoring). They are qualified for this reason as leadless, to distinguish them from the electrodes disposed at the distal end of a conventional lead (lead), crossed along its entire length by one or more conductors galvanically connecting the distal electrode to a connector located at the opposite, proximal end of the lead, the connector being intended to be connected to the housing of the pulse generator.
These leadless capsules can advantageously replace conventional endocardial leads such as right ventricular and right atrial leads, or the epicardial leads, but because of their size they cannot be substituted for the stimulation of the left ventricle to leads introduced into the coronary venous system, leads which are required for detection/stimulation of the left ventricle, therefore the application of a CRT therapy. In addition, the endocardial arterial network (thus providing access to the left cavities) remains extremely risky, even with a leadless capsule, because of the serious risk of bleeding or blood clots, which can form arterial emboli.
On the other hand, with regards to the left coronary leads, the need for a guidewire to be used for implantation, the standard norm of the multipolar left lead connectors (IS-4 or DF-4 standards) and the need for a central lumen formed in the lead body for the introduction of the guidewire, are constraints that limit the ability to reduce the diameter of the coronary leads and therefore to reach new target areas of stimulation of the left ventricle that remain difficult to reach today.
U.S. Pat. No. 7,634,313 B1 describes a biventricular pacing system combining:                For stimulation of the right ventricle, a conventional pacemaker with a generator housing connected to an also conventional endocardial lead, and        For stimulation of the left ventricle, an epicardial leadless capsule implanted on the outer wall of the left ventricle and communicating by wireless link with the generator, the latter playing a role of the master and the leadless capsule that of the satellite.        
With this system, however, the problems mentioned above remain, as well as those specific to conventional pacemakers (generator volume, difficulty reaching the coronary sinus with the lead, implantation with guidewire delivery system, etc.) and, finally, need for intervention by transthoracic approach for implantation of the epicardial capsule.
The aim of the invention is to propose a device that overcomes the various drawbacks exposed above.